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Numerical Study of the Effects of Drainage Systems on Saturated/Unsaturated Seepage and Stability of Tailings Dams

Numerische Studie über die Auswirkungen eines Entwässerungssystems an gesättigten und ungesättigten Sickerwasserlinien und die Stabilität von Dämmen

Estudio numérico de los efectos de los sistemas de drenaje sobre la infiltración satura/insaturada y la estabilidad de los diques de cola

数值模拟研究尾矿坝排水系统对坝内饱和/包气渗流及坝体稳定性的影响

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Abstract

The stability of tailings dams is affected by seepage characteristics such as the location of the phreatic surface inside the dam, the effects of the capillary fringe, and the unsaturated zone above the zero pore pressure level. In this study, the performance of drainage systems in tailings dams was investigated by analyzing saturated and unsaturated seepage in the dam, considering the effects of the construction method, tailings properties, and the type of drainage systems. First, general seepage characteristics in tailings dams were studied and the effects of non-homogeneity were investigated. Our results show that in a silty tailings dam with a height of 15 m, unsaturated plus capillary seepage flux can reach 13% of the total seepage. The total head vs. discharge volume curves under various conditions were compared and their practical implications are presented. Then, stability analyses were carried out using the results of seepage analyses for different construction methods, material properties, and drainage systems. Finally, a number of practical conclusions are drawn regarding dam stability and the efficiency of toe, blanket, and chimney drains in different construction methods. Using a blanket and/or a chimney drain can increase the stability safety factor by up to two times, depending on the type of material.

Zusammenfassung

Die Stabilität von Absetzbecken ist beeinflusst durch die Eigenschaften des Sickerwassers wie die Lage der Sickerlinie im Damm, die Auswirkungen des Kapillarsaums und die ungesättigte Zone oberhalb des 0-Porendrucks. In dieser Studie wurde die Wirkung eines Entwässerungssystems in Dämmen untersucht durch Analyse der gesättigten und ungesättigten Sickerwasserzonen im Absetzbecken. Dabei wurden die Auswirkungen der Konstruktionsmethode, Schlammeigenschaften und die Art des Entwässerungssystems beachtet. Zuerst wurden die Sickereigenschaften im Absetzbecken und die Inhomogenitäten untersucht. Unser Ergebnis zeigt, dass bei einem schlammigen Absetzteich mit einer Höhe von 15 m, der Sickerwasserabfluß ca. 13% der ungesättigten Zone und des Kapillarsaum erreichen kann. Die Gesamthöhe der Entwässerungskurven wurden unter verschiedenen Bedingungen verglichen und ihre praktischen Auswirkungen dargestellt. Danach wurden Stabilitäts-Analysen durchgeführt, indem die Ergebnisse der Sickerwasser-Analysen für verschiedene Konstruktionsmethoden, Materialeigenschaften und Entwässerungssysteme berücksichtigt wurden. Letztendes konnten eine Anzahl praktischer Schlussfolgerungen gezogen werden, welche die Stabilität des Dammes und die Effizienz von Abdichtung, der Überdeckung sowie der Entwässerungskanäle in unterschiedlichen Konstruktionsmethoden betreffen. Durch die Art der Überdeckung und Entwässerungskanäle kann der Stabilitätsfaktor, abhängig vom verwendeten Material, verdoppelt werden.

Resumen

La estabilidad de los diques de cola es afectada por las características de las infiltraciones como la localización de la superficie freática dentro del dique, los efectos de la franja capilar, y la zona insaturada debajo del nivel de presión de poro cero. En este estudio, se investigó el comportamiento de los sistemas de drenaje en diques de cola por análisis de las infiltraciones saturadas e insaturadas en el dique considerando los efectos del método de construcción, las propiedades de las colas y el tipo de sistema de drenaje. Primero, se estudiaron las características de las infiltraciones generales en el dique y los efectos de la no homegeneidad. Los resultados muestran que en un dique de colas con una altura de 15 m, la infiltración insaturada y la capilar pueden alcanzar un 13% del total. Se compararon las curvas de cabeza versus volumen de descarga bajo varias condiciones y sus implicancias prácticas se presentan en este trabajo. Luego, se realizaron análisis de estabilidad usando los análisis de iinfiltraciones para diferentes métodos de construcción, propiedades de materiales y sistemas de drenaje. Finalmente, se elaboraron conclusiones prácticas respecto de la estabilidad del dique y la eficiencia de los drenajes tipo chimenea, base o manta en diferentes métodos de construcción. Usando un drenaje tipo manta o tipo chimenea puede incrementarse la estabilidad hasta el doble dependiendo del tipo de material.

抽象

尾矿坝体稳定性受坝体内潜水面位置、毛润前锋、零孔隙压力以上非饱和带等渗流特征影响。考虑坝体堆积方法、尾矿特性和排水系统类型,分析了尾矿坝内饱和与非饱和渗流特征,研究了尾矿坝排水系统的功能状况。首先,研究了尾矿坝内渗流总体特征及非均质特性。15m高粉质粘土尾矿坝非饱和正毛细渗流通量可达总渗流通量的13%,同时对比了多种条件下总水头~总排水量关系曲线及含义。然后,依据不同堆积方法、材料性能和排水系统的渗流特征分析坝体稳定性。最后,得到不同堆积方式下墙趾、垫层、土坝垂直排水系统的排水效率和坝体稳定性。依据坝体材料不同,采用垫层和/或垂直排水系统能将坝体稳定性安全因子提高近2倍。

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Pak, A., Nabipour, M. Numerical Study of the Effects of Drainage Systems on Saturated/Unsaturated Seepage and Stability of Tailings Dams. Mine Water Environ 36, 341–355 (2017). https://doi.org/10.1007/s10230-017-0468-y

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